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I6 4.0L Rear Main Seal


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I've had my MJ for four months and I've done all kinds of repairs on parts that did and might not have needed replacing. I don't know the history of my beauty and I want her to last for ever and ever. My plan is to replace everything that turns, moves, rots, or rolls. I've done all the tie rods, ball joints, shocks, hubs, wheel bearings, U Joints, all new brake system including the lines, all the fluids, every component connected to the serpentine belt (it was the alternator with the squeak to my surprise), and more, and more. I've spent over $4,000 with Rock Auto in the past four months and done all my own labor. I have a slow ongoing saga about the dummy to full cluster swap and I'm nearing the end of that adventure that started with a broken speedometer cable.

 

In my quest to change all this, of course I replaced the Rear Main Engine Seal. OK, it was leaking, and I thought I did a good job, but it began to leak and leak more and faster for every minute she ran. Yes, I did understand what the little shoe horn was for. I went back into the articles and then noticed comments like... If you've never done it before, buy two seals, and so forth. I just can't bring myself to drop the oil pan again and try to figure out what I did wrong and roll that dice again.

 

I looked for a local Jeep specialist, and found nothing to my surprise. We take my wife's Beetle to a private shop that only services all models and years of and only VWs. I can't believe I didn't find such a thing for the Jeep. There is a local shop that does high-end custom builds and has a top notch reputation. The Pros. Not Cheap! With the new seal in hand, I decided to take her there.

 

They haven't ever done a 4.0L seal, and being who they are, they know everyone in the business, including THE Local Guru, now retired and in his mid-70's. They told me this story of this Guru having his own shop years ago with 10 Jeeps on lifts at the same time and he was working on them all in an assembly line fashion - Just Him - working on them all at the same time. After the MJ has been sitting there for a couple days and them doing their research, they talk to the Guru. I then get a call and I'm told... "OK, the Guru is going to come over and take care of this and show us all how to do it. We're all very interested to see it. What we need from you is a piece of carbon paper. That's the trick and it will never leak again".

 

I'm like "Carbon Paper". They're like, yes, "Carbon Paper". Well, nobody sells carbon paper so I ordered it on Amazon and hope it comes tomorrow. When it does, I'll rush it over and have them call the Guru. I just hope I get to see what the Guru does with the carbon paper. Now I'm wondering about the articles I've read where somebody claims to have replaced 25 rear main seals and wonder how many of them were on the same engine because they didn't use carbon paper.

 

Bewildered and Curious about Carbon Paper in Maryland

Romain

 

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I'm very curious about the carbon paper too.  I had one 4.0 RMS that was so coked in I destroyed the brass punch.  I had to use a regular punch to get it moving.  That was a high pucker experience as the crank wouldn't have been happy if it had slipped.

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On 4/30/2021 at 1:21 AM, ghetdjc320 said:

I could see that being where the carbon paper comes into play possibly. 

For the sealant?  I was thinking about wiping the seal with it to lube it up (Dry lube, it's basically graphite on the paper) prior to installing it.

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9 hours ago, Tex06 said:

For the sealant?  I was thinking about wiping the seal with it to lube it up (Dry lube, it's basically graphite on the paper) prior to installing it.


Yep that would make sense. Though nowadays graphite lube is easier to find than carbon paper lol

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My MJ was wrapped up today. We're just waiting for the gasket sealant to dry overnight, fill with oil and test for leaks in the morning.

 

I met George (the Guru) today when they were closing up and torquing everything down. I asked about it all and the following is from my understanding and I make no guarantee as to it's accuracy as I didn't see it all go together.

 

First, he did not use the Fel-Pro seal I provided. Instead, he used an Apex seal that has a bigger lip and is thicker and more durable (so I hear). The thicker Apex seal makes a tighter seal for the top. Second, gasket maker went in the rear bearing cap under the lower portion of the Apex seal. Third, the carbon paper went between the rear bearing cap and the bearing. This better secures the rear bearing to make a more snug seal on the crank shaft and thus out through to the seal. An ever so slightly wobbling shaft wears out the seal and allows oil to leak through. The carbon paper is thin, just enough to make up for wear from the miles to correct the spacing wear in there. The carbon is also efficient in resistance to heat and oil. Finally, he put gasket maker at the union of the seal and torqued down the rear bearing cap and were finishing closing her up when I arrived. George guaranteed there will be no leaks as he's done thousands of them.

 

After spending four months laying on the driveway in the coldest months of the year looking up from there, it was nice to see her on the lift.

 

I will try to update this thread when it starts leaking again... hopefully about 20 years from now.

-Romain

 

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21 minutes ago, ghetdjc320 said:

So basically he used the carbon paper in lieu of a repair sleeve it sounds like correct? Makes sense if your crank was worn. I’ve always had a new crank going in at the same time. 

That's how I take it. Since it's not a rebuild and just a seal replacement, that's what it seemed to be for.

Romain

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16 hours ago, ghetdjc320 said:

So basically he used the carbon paper in lieu of a repair sleeve it sounds like correct? Makes sense if your crank was worn. I’ve always had a new crank going in at the same time. 

Ok, that tracks. Cool little backwoods type repair....you know what they say: "If it's stupid but works, it ain't stupid". I'll have to file that one back in the cool tips and tricks folder in my head.

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  • 4 weeks later...
  • 4 months later...
On 5/3/2021 at 8:34 PM, ghetdjc320 said:

So basically he used the carbon paper in lieu of a repair sleeve it sounds like correct? Makes sense if your crank was worn. I’ve always had a new crank going in at the same time. 

 

Sounds more like he used the carbon paper as a shim for the rear main bearing itself, instead of just replacing the bearing.

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